Road prisms are low-profile optical targets used to monitor settlement and deformation of roads, pavement, and other surfaces. GEO-Instruments offers a polymer version and a cast-aluminum version. Datasheet
Polymer Road Prism
The polymer road prism features a low-profile, non-reflective black housing that is nearly invisible to drivers. It is available with prisms set at 10, 20 or 40 degrees to achieve the best match with the elevation of the AMTS. No drilling is needed for installation.
- Clean the surface.
- Apply FHWA / AASHTO approved adhesive to the surface.
- Align the prism toward the total station.
- Press prism onto adhesive.
Dimensions: 3.9″ diameter x 0.7″ height ( 100 x 18 mm).
Materials: Injection molded polymer dome, optical glass prism.
Prism: 0.4 inch (10 mm) diameter.
Prism Angle: Choice of 10°, 20°, or 40°.
Prism Offset: -13.1 mm for Topcon, Trimble, etc. +21.3 mm for Leica.
Aluminum Road Prism
The aluminum road prism features a heavy-duty, cast-aluminum housing made to withstand heavy machinery. It is installed with screws which help keep the prism in place during repeated freeze-thaw cycles. It is available with a single prism or a double prism (180° opposed).
- Clean the surface.
- Align prism toward total station and mark position for drill holes.
- Clean the holes and inject epoxy mortar into drill holes.
- Place prism over holes and screw down.
Dimensions: 4 x 4 x 1 inch (100 x 100 x 23 mm).
Materials: Cast aluminum housing and stud, optical glass prism.
Prism: 0.7 inch (17 mm) diameter. Double sided unit has two prisms.
Prism Angle: 20°.
Prism Offset: -11.3 mm for Topcon, Trimble, etc. +23.1 mm for Leica.
Prisms can accommodate misalignments of ± 10°. For example, the 20° prism can provide accurate measurements with angles between 10° to 30°. In typical scenarios, 10° prisms are used with AMTS mounted on pedestals or tripods. 20° prisms are used with AMTS mounted on buildings up to 3 to 5 stories high, and 40° prisms are used with AMTS mounted on buildings 10+ stories high.